In November 2007 the British Trust for Ornithology in partnership with the Scottish Ornithologists' Club and Birdwatch Ireland is starting a four year winter and breeding season atlas project aimed at revising the distribution maps and population estimates from the 1981-84 Winter Atlas and the 1988-92 Breeding Atlas. The winter season will span the months of November to February inclusive and for most species the breeding season will be considered to extend from the start of April to the end of July.
The methodology for the UK and Ireland will comprise two components: Roving Records and Timed Tetrad Visits.
The Roving Records method will aim to build complete species lists for each 10km square. During the breeding season additional behavioural data will be collected to assign possible, probable or confirmed breeding status on the basis of standard criteria.
The Herts Bird Club project will operate under the same methodology, but will capture information at the scale of a tetrad (2km x 2km square). This will cover all 491 tetrads which include part of the county of Hertfordshire.
For Timed Tetrad Visits, the expectation is that two visits will be made to a minimum of eight tetrads in each 10km square in each season. That is a total of 32 field visits which can be spread across the four years. This should be easily attainable in a densely populated county like Hertfordshire, but we still need volunteers to sign up for tetrads. Each visit will need to last at least one hour, preferably two hours, with an option to extend beyond that. It is expected that during that time a representative sample of the available habitat will be covered. During these visits the emphasis will be on counting all birds observed, as this data will primarily be used to determine abundance.